Linolenate 9R-dioxygenase and allene oxide synthase activities of Lasiodiplodia theobromae

Lipids. 2012 Jan;47(1):65-73. doi: 10.1007/s11745-011-3622-5. Epub 2011 Nov 3.

Abstract

Jasmonic acid (JA) is synthesized from linolenic acid (18:3n-3) by sequential action of 13-lipoxygenase, allene oxide synthase (AOS), and allene oxide cyclase. The fungus Lasiodiplodia theobromae can produce large amounts of JA and was recently reported to form the JA precursor 12-oxophytodienoic acid. The objective of our study was to characterize the fatty acid dioxygenase activities of this fungus. Two strains of L. theobromae with low JA secretion (~0.2 mg/L medium) oxygenated 18:3n-3 to 5,8-dihydroxy-9Z,12Z,15Z-octadecatrienoic acid as well as 9R-hydroperoxy-10E,12Z,15Z-octadecatrienoic acid, which was metabolized by an AOS activity into 9-hydroxy-10-oxo-12Z,15Z-octadecadienoic acid. Analogous conversions were observed with linoleic acid (18:2n-6). Studies using [11S-(2)H]18:2n-6 revealed that the putative 9R-dioxygenase catalyzed stereospecific removal of the 11R hydrogen followed by suprafacial attack of dioxygen at C-9. Mycelia from these strains of L. theobromae contained 18:2n-6 as the major polyunsaturated acid but lacked 18:3n-3. A third strain with a high secretion of JA (~200 mg/L) contained 18:3n-3 as a major fatty acid and produced 5,8-dihydroxy-9Z,12Z,15Z-octadecatrienoic acid from added 18:3n-3. This strain also lacked the JA biosynthetic enzymes present in higher plants.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Ascomycota / enzymology*
  • Chromatography, Reverse-Phase
  • Cyclopentanes / metabolism*
  • Dioxygenases / metabolism*
  • Fatty Acids, Unsaturated / metabolism
  • Intramolecular Oxidoreductases / metabolism*
  • Linoleic Acid / metabolism
  • Lipid Metabolism*
  • Lipoxygenase / metabolism
  • Mycelium / enzymology*
  • Oxylipins / metabolism*
  • Plant Growth Regulators / biosynthesis*
  • Plants / microbiology
  • Tandem Mass Spectrometry
  • alpha-Linolenic Acid / metabolism

Substances

  • Cyclopentanes
  • Fatty Acids, Unsaturated
  • Oxylipins
  • Plant Growth Regulators
  • hydroxyoctadecadienoic acid
  • alpha-Linolenic Acid
  • octadecadienoic acid
  • jasmonic acid
  • Linoleic Acid
  • 13-lipoxygenase
  • Dioxygenases
  • Lipoxygenase
  • Intramolecular Oxidoreductases
  • hydroperoxide isomerase